Haible Subtle Chorus

[Davebassman]

Hi,

I found some of this boards in my house... 2010! And I will try to build it. But I have some questions.

http://jhaible.com/legacy/subtle_cho...le_chorus.html

You can build the vintage version with HA1457W ( obsolet ) or the modern with standard TL072. And with or without power transistors.

What is the difference of building the version with or without power transistors?

In the BOM of the main board say ( vintage )

HA1457W:

Vintage OpAmp in SIL package. If you don't find these, you
can build a modern version with TL072's (and without power
transitors) - there's a different BOM for this version.
Or, if you want to use the power transitor output stage
without HA1457W's, try other Dual OpAmps in the DIL8
package. I'm sure there are some that will work. (TL072's will
not work in that configuration - there's oscillation on
capacitive load!)

The question is. Worth build the modern version with power transistors? in this case, what IC I can try to avoid this oscillation?

Thanks.

P.D.: I've read somewhere that there are a Burr Brown IC that is very similar to the HA1457W. OPA604 maybe?

[Mick Bailey]

It appears that the build with the transistor output is to drive a low-impedance load, which the original opamps would struggle to do (class A operation is shown as 10K Ohm in the data sheet). So if you have long cable lengths feeding a low-impedance desk input you'd perhaps want the transistor version. I had a mixer in for repair that was stuffed with those SIL ICs and found them quite cheaply at the time (6 years ago), but they may be harder to find now. There are expensive conversion boards for TL072s that allow pin compatibility - it may be worth looking at how these are implemented and doing more research into equivalents. Could be a little bit of trial and error with opamp types.

[Davebassman]

It appears that the build with the transistor output is to drive a low-impedance load, which the original opamps would struggle to do (class A operation is shown as 10K Ohm in the data sheet). So if you have long cable lengths feeding a low-impedance desk input you'd perhaps want the transistor version. I had a mixer in for repair that was stuffed with those SIL ICs and found them quite cheaply at the time (6 years ago), but they may be harder to find now. There are expensive conversion boards for TL072s that allow pin compatibility - it may be worth looking at how these are implemented and doing more research into equivalents. Could be a little bit of trial and error with opamp types.

Thanks for the clarification. I try to find the HA1457W. I think this will be less expensive thant this tl072 adaptors.

[g1]

I try to find the HA1457W. I think this will be less expensive thant this tl072 adaptors.

Smallbear electronics has them.

[nosaj]

Smallbear electronics has them.

Is he still in business?
nosaj

[The Dude]

The website is still up.

https://smallbear-electronics.mybigc..._query=HA1457W

It looks like the company has changed hands, but is still running.

https://smallbear-electronics.mybigc...ut-small-bear/

[Mick Bailey]

For guitar use feeding into a regular 1M Ohm input amp, or into another FX unit with maybe lower impedance of half that, the TL072 version is fine and works out as the least complex and most inexpensive build. Oscillation driving capacitive loads with a TL072 can be prevented by adding a compensating series resistor in the output - there's a TI paper on this somewhere, but this would require modifying the boards.

[Davebassman]

For guitar use feeding into a regular 1M Ohm input amp, or into another FX unit with maybe lower impedance of half that, the TL072 version is fine and works out as the least complex and most inexpensive build. Oscillation driving capacitive loads with a TL072 can be prevented by adding a compensating series resistor in the output - there's a TI paper on this somewhere, but this would require modifying the boards.

I want this unit for use in my studio, vocals, acoustics, etc... so I need a line level output. I ordered 12x HA1457W from smallbear. I only use them with the main board, with the bbd board I use common TL072

[Davebassman]

It appears that the build with the transistor output is to drive a low-impedance load, which the original opamps would struggle to do (class A operation is shown as 10K Ohm in the data sheet). So if you have long cable lengths feeding a low-impedance desk input you'd perhaps want the transistor version. I had a mixer in for repair that was stuffed with those SIL ICs and found them quite cheaply at the time (6 years ago), but they may be harder to find now. There are expensive conversion boards for TL072s that allow pin compatibility - it may be worth looking at how these are implemented and doing more research into equivalents. Could be a little bit of trial and error with opamp types.

Would by fine use the HA1457W only for the mainboard and TL072 for the BBD board? to avoid this oscillation? or is mandatory use the HA1457W for the two boards?